The hole at the bottom of the Gulf of Mexico may be plugged, but the problems aren’t over. There’s still a lot of oil in the water. Scientists are trying to find and remove it — and that’s a difficult process.

On April 20, the Deepwater Horizon drilling platform exploded. It sank two days later. A long pipe connected the drilling platform to an oil well buried deep under the Gulf of Mexico. When the platform sank, the pipe crumpled and oil began to flow into the water.